Function
What you will find in this section:
Function
The Modbus protocol defines both a protocol on the application layer and a transmission protocol. The application layer protocol is identical for all interface versions. The differences between Modbus/TCP and Modbus/RTU lie in the transmission protocol.
On the application layer, Modbus supplies a 16-bit address space that can be used to address 16-bit registers. Using various function codes, read and write operations can be performed on registers.
For detailed information about the Modbus specification refer to www.modbus.org.
The EMpro supports the following function codes:
- 03 (0x03) Read holding registers
- 04 (0x04) Read input registers
- 06 (0x06) Write single register
- 16 (0x10) Write multiple registers
Here, it has to be noted that the device does not differentiate between holding and input registers. Both function codes return the same registers.
To change settings via the Modbus interface sustainably the following procedure must be followed
- PIN entry (register 16403)
- Write register which should be changed
- Accepting the configuration (write „1“ in register 16387)
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